Many American shoppers may have a costly hangover in the new year, according to a new retail survey.

An astonishing 9 out of 10 respondents to a survey by The Checkout are “impulse purchasers,” buying goods not on their shopping lists. That’s as much as $200 monthly in additional credit-card charges for the average US shopper for purchases on a whim.

And 71 percent of consumers polled recently by Harris Interactive have regretted buying goods on impulse.

Retail experts say that means plenty of returned holiday merchandise in 2013. And more junk for the next garage sale.

“When people impulse buy, they just think about the amount they’ve spent that day, but really, every impulse purchase has this long-term ramification,” said Patricia Seaman of Harris Interactive.

Of American consumers who have made impulse purchases they have regretted in the past 12 months, the Harris Interactive survey showed:

* 47 percent spent it on clothing and shoes. (Some 60 percent of women are more likely to say this, compared with 34 percent of men.)

“You get that visceral reaction because something happened in your day, maybe. You’re feeling bad about something, and you want to feel better.”

But after feeling better, many consumers later regret their spontaneous purchases. And that regret is likely to stretch well into the new year, with the typical flourish of sales and store discounts in the coming weeks. Some 50 percent of impulse purchases by American adults were triggered by sales and discounts, according to the Harris Interactive poll.